This invention relates in general to vehicle electric power steering assemblies and in particular to an improved rack drive assembly adapted for use in such a vehicle electric power steering assembly.
One known electric power steering assembly for turning steerable wheels of a vehicle includes a ball nut for transmitting force between an axially movable rack member and an electric motor. Upon actuation of the electric motor of the power steering assembly, the ball nut is driven to rotate relative to the rack member. The rotational force of the ball nut is transmitted to the rack member by balls to drive the rack member axially. The axial movement of the rack member by the balls effects turning movement of the steerable wheels.
The electric motor in the above-described electric power steering assembly can be coupled to drive the ball nut in various known methods. One such method includes a belt drive assembly wherein an output shaft of the electric motor is connected via a belt to a pulley assembly. The pulley assembly typically includes a pulley which is operatively fixed to the ball nut so that the ball nut rotates with the pulley when the electric motor is actuated. This type of electric power steering assembly has advantages over other known electric power steering assemblies. However, in this type of electric power steering assembly, one or more disadvantages may be in the overall size, cost, packaging and/or operating characteristics of one or more of the components of the rack drive assembly, in particular of the pulley assembly and/or the ball nut assembly, may not be desirable or optimal.
Thus, it would be desirable to provide an improved structure for a rack drive assembly of an electric power steering assembly which reduces and/or improves upon one or more of the above disadvantages and is relatively simple and inexpensive.